The present invention will be described for determining whether a size of a spark plug gap is within an acceptable range during manufacture of a vehicle engine. However, the present invention may be used for determining whether the size of a gap formed by two conductive nodes within any type of component assembled into any type of article of manufacture is within an acceptable range during assembly of the article of manufacture, as would be apparent to one of ordinary skill in the art from the description herein.
Referring to FIG. 1, a spark plug 102 is installed into a vehicle engine 104. FIG. 1 shows a cut-away view of a portion of the vehicle engine 104 having the spark plug 102 installed therein. A spark plug, which is a common component of a combustion engine, has a spark plug gap which electrically bridges for running the combustion engine, as known to one of ordinary skill in the art. Referring to FIG. 1, the spark plug 102 has a first conductive node 106 and a second conductive node 108. The spark plug gap of the spark plug 102 is the space between the first conductive node 106 and the second conductive node 108. The first conductive node 106 is conductively coupled to a top conductive node 107.
In the modem assembly line for manufacture of vehicle engines, a spark plug is installed within a spark plug chamber 110 of the vehicle engine 104 with an automated robotic system. During the assembly of the vehicle engine 104, the first conductive node 106 and the second conductive node 108 at the tip of the spark plug 102 may be accidentally smashed together. Thus, the size of the spark plug gap formed by the first conductive node 106 and the second conductive node 108 may then become undesirably smaller than an acceptable range. When the size of the spark plug gap is smaller than the acceptable range, the vehicle engine 104 may misfire and/or may run rough.
In a typical prior art assembly line for manufacture of vehicle engines, the vehicle engine 104 is not run until a relatively long time after the spark plug 102 has been installed into the vehicle engine 104 since many other components are also assembled into the vehicle engine 104 before the vehicle engine may be run. Thus, the size of the spark plug gap may not be readily checked at or near the location for installing the spark plug within the assembly line for manufacture of the vehicle engine 104. However, corrective measures for dealing with a defective spark plug may be most efficiently performed at or near the location for installing spark plugs within the assembly line for manufacture of the vehicle engine 104.
Thus, a system is desired for checking the size of the spark plug gap 102 that has been installed into a vehicle engine 104 at or near the location for installing spark plugs within the assembly line for manufacture of the vehicle engine 104. Such a system effectively checks for the size of the spark plug gap during assembly of the vehicle engine, and thus does not require a running vehicle engine that is completely assembled.
In contrast, unfortunately, the prior art systems for checking or monitoring the spark plug gap, such as U.S. Pat. No. 3,904,955 to Katz and U.S. Pat. No. 5,491,416 to Klimstra et al. depend on the wiring of a running combustion engine that is completely assembled. Thus, these prior art systems may not be amenable for checking the size of the gap of a spark plug assembled into a vehicle engine at or near the location for installing the spark plug before the vehicle engine has been completely assembled.
U.S. Pat. No. 4,024,469 to Bobulski discloses an apparatus for measuring spark plug gap spacing by applying an AC voltage across the spark plug gap and then measuring the time from the zero-crossing of this AC voltage to the time point of the spark plug firing. However, such an apparatus of the prior art uses predominantly analog components such as numerous differential amplifiers. Thus, this prior art apparatus does not disclose the use of a microcontroller for a more flexible and reliable checking of the size of a spark plug gap during assembly of an article of manufacture.